Exam Average 78.4 Median 84

Outline Applications of Gauss’s Law - The single Fixed Charge -Field of a sphere of charge -Field of a spherical shell -A Line of Charge Conductors and Insulators The electric field of a conductor The field in the cavity of a conductor; Faraday’s Cage

Gauss’s Law The total flux of electric field out of any closed surface is equal to the charge contained inside the surface divided by.

A Charged, Thin Sheet of Insulating Material

Conductors and insulators Charges reside at the surface of the conductor Conductor E=

There is no electric field inside a conductor Net charge can only reside on the surface of a conductor Any external electric field lines are perpendicular to the surface (there is no component of electric field that is tangent to the surface). The electric potential within a conductor is constant

since inside the conductor. For any two points and inside the conductor The conductor’s surface is an equipotential.

Equipotential Surfaces An equipotential surface is a surface on which the electric potential V is the same at every point. Because potential energy does not change as a test charge moves over an equipotential surface, the electric field can do no work on such a charge. So, electric field must be perpendicular to the surface at every point so that the electric force is always perpendicular to the displacement of a charge moving on the surface. Field lines and equipotential surfaces are always mutually perpendicular.

A field in a cavity of a conductor Faraday’s cage

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